This invention relates to a vent system for an electric storage battery, and more specifically to a vent plug system which is designed to separate the entrained electrolyte from gases which are vented from the battery cells to the atmosphere through the vent plug.
In reading the following disclosure, it should be noted that the invention disclosed and claimed herein, and the discussion concerning it, are applicable to many kinds of battery systems, and that the references to applications in the area of automotive batteries and maintenance free automotive batteries are made to illustrate possible uses of the invention and not for the purpose of limiting the scope of the claimed invention.
When designing a vent plug for use with a maintenance free battery, there are several important considerations. Ideally, a maintenance free battery is designed so that throughout its normal life, no service is required, such as the addition of water to the battery cells. Since most maintenance free batteries do consume some water, the battery design is such that a sufficient reserve of electrolyte is provided by having the liquid level of the electrolyte as high as possible in a new battery.
The requirement for a high electrolyte liquid level imposes new limitations on a design for a vent plug. One limitation is that the physical size of the vent plug is restricted so that the distance the vent plug extends into the vent well of a particular cell is minimized, thereby allowing a maximum liquid level height. Second, the vent plug should be designed so that in the event the electrolyte liquid level rises to a point where the bottom of the vent plug is in contact with the electrolyte, any pressure which may develop in the particular battery cell can still be relieved.
One method of further reducing the amount of electrolyte or water loss during the operation of the battery, is to scrub the fluid that is vented so that the gaseous phase and the liquid phase are separated and the liquid phase is returned to the individual cell. Failure to do otherwise may result in a maintenance free battery with a potentially shorter life due to excessive loss of electrolyte as well as acid contamination of the outside of the battery.
Designing a vent plug which will meet these considerations is further complicated when marketing requirements demand that the vent plugs not extend above the upper surface of the battery cover so that the battery is aesthetically pleasing to the consumer and has the appearance of a maintenance free battery. The resulting design for such a vent plug must therefore have a low profile, with an efficient liquid gas separation system designed to operate properly even though the liquid level of the electrolyte has risen enough to cover the bottom portion of the vent plug.